Isolation, Biological Activities and Synthesis of Indoloquinoline Alkaloids: Cryptolepine, Isocryptolepine and Neocryptolepine

The tetracyclic heteroaromatic compounds cryptolepine, isocryptolepine and neocryptolepine are all naturally occurring indoloquinoline alkaloids isolated from the shrub Cryptolepis sanguinolenta and are important due to their wide spectrum of biological properties. This review describes the isolation, brief biological activities and various synthetic methodologies developed during recent years for the preparation of this important class of alkaloids, with special emphasis on preparation and properties of cryptolepine 1, isocryptolepine 2 and neocryptolepine 3.